This application is based on the application No. 2001-354944 filed in Japan, the content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a blood component measurement apparatus such as a pulse oximeter.
2. Related Art of the Invention
In a blood component measurement apparatus such as a pulse oximeter, a light emitting element emits light. The light transmitted through a subject body (the body of a subject person) is then measured by an electric circuit comprising a photodetector, whereby oxygen saturation or the like of the blood is obtained.
Nevertheless, in such a blood component measurement apparatus, the measurement signal can contain periodic noise, such as induced noise of line frequency and that due to light from fluorescent lamps. Thus, since the level of the measurement signal of the transmitted light detected by the photodetector is very low, the influence of such periodic noise needs to be eliminated in order that the blood component is measured precisely.
The invention has been devised to resolve this problem. The object of the invention is to provide a blood component measurement apparatus for measuring a blood component precisely.
In order to resolve the above-mentioned problem, a blood component measurement apparatus for measuring a blood component in the arterial blood of a subject body according to the invention comprises: an illuminating device for illuminating said subject body with predetermined light periodically at first timings; a light intensity detector for detecting light intensity measurement values of light transmitted through said subject body; a dark level detector for detecting dark level measurement values periodically at second timings without illumination from said illuminating device; a pulse wave detector for extracting pulse wave component from said light intensity measurement values, and thereby detecting pulse wave measurement values; and a blood component measurer for measuring the blood component of said arterial blood on the basis of said light intensity measurement values, said dark level measurement values, and said pulse wave measurement values; wherein each time interval between said first timings and said second timings corresponds to a line frequency.
In the following description, like parts are designated by like reference numbers throughout the several drawings.